Why Are Plow Plane Irons So Tapered?

I have this odd hankering to try building a plow plane. Only twist is that I do not have any irons for one, which is not typical of someone looking to build one. I was planning to just make my own out of O1 stock, but would greatly prefer to not taper the irons. Why are they so tapered? Is it mostly so that the iron position doesn’t change through the cut (wedging the iron deeper the harder it’s engaged)? There are so many wedged planes with non-tapered irons that I can’t see why it wouldn’t work with a plow plane. I’ve never even used one, though, so I can’t say for sure. What say ye?

I don’t know of any old wooden plows that were commercially made that don’t have tapered irons. There are metal ones that lack tapered irons. Most people don’t seem to understand there was no standard as to taper and fit to the plane and old plow planes vary widely. Finding irons to fit an old plane is difficult at best. Even irons from the same maker but made in a different run will vary. Most the “sets” of plow irons out there are assembled sets that don’t really match each other.

The amount of taper in these irons isn’t as severe as they appear. The actual taper is what is between the bottom of the groove to the flat face. The rest of the apparent taper houses the groove which fits a mating angled front of the skate. The fit of this groove to the skate is pretty critical. The angles have to match because they give lateral stability to the iron which is needed for heavier cuts usually used with plow planes. These mating angles act similar to a Morris or other taper found in machines.

The depth of the groove, the amount of taper, the distance from the groove to the flat face, the location of the groove, and the width of the blades tang are just some of the variables in old irons. Plow planes are made to fit the set of matching irons, not the other way around as in metal mass produced planes.

Well, then I will likely go with no taper. I understand the physics, I was just wondering if there were any other considerations and if it is feasible to go with no taper, as that would be significantly greater work on my part. This project is on the back burner for a while, but I have some lovely 12/4 black walnut stock just waiting for it.